1. Field of the Invention
The present invention relates to a steering apparatus for a car which is capable of inclining a steering wheel to perform a tilt adjustment, and axially moving the steering wheel to perform a telescopic adjustment of the axial position thereof, and more specifically, to a steering apparatus for a car which is capable of enhancing the rigidity of a steering column, or the like, by positively preventing a backlash of the steering column, or the like, and obtaining an excellent operability for telescopic adjustment by decreasing the operating force of telescopic adjustment, so as to reduce the processing cost.
2. Related Background Art
In Japanese Utility Model Publication No. 2-24366, there is disclosed a steering apparatus for a car which can perform a tilt adjustment of the steering wheel as well as a telescopic adjustment of the length of the steering apparatus by moving the steering wheel in the axial direction. A steering apparatus constituted in accordance with this publication is shown in FIG. 7. Referring to FIG. 7, a spline shaft 3 is spline-fitted in a lower part of a steering shaft 1 which is supported to be freely rotatable by a steering column 2, and a universal joint 4 is coupled to a lower part of this spline shaft 3.
The steering column 2 is provided with an upper bracket 5 fixed to the car body and a distance bracket 6. A fastening bolt 9 with an operating lever 10 is inserted through two holes, that is, an elongated hole 7 for tilt adjustment formed on this upper bracket 5 and an elongated hole 8 for telescopic adjustment formed on the distance bracket 6.
An outer tube 11 is attached to a lower part of the steering column 2, and a spherical bush 12 is fitted on the outer periphery of the outer tube 11. A bush holder 13 slidably in contact to this spherical bush 12 is mounted on a lower bracket 14 fixed to the car body. An O-ring 15 is fitted in a groove which is formed on the top of the spherical bush 12. This O-ring 15 not only comes in tight contact with the bush holder 13, but also brings the inner peripheral surface of the spherical bush 12 into tight contact with the outer peripheral surface of the outer tube 11 to fasten together. Since the spherical bush 12 and the O-ring 15 are brought into slidable contact with the bush holder 13 as described above, a backlash or the like which may be caused by vibration of the steering wheel or the like in a high-speed running can be prevented.
In the steering apparatus as mentioned above, when the steering wheel is to be subjected to a tilt adjustment, if the operating lever 10 is loosened, the steering shaft 1 and the steering column 2 are inclined and, at the same time, the fastening bolt 9 is guided along the elongated hole 7 for tilt adjustment of the distance bracket 6. On this occasion, if the axial length of the steering shaft 1 is also required to be finely adjusted, the steering shaft 1 which is spline-fitted in the spline shaft 3 is moved in the axial direction with respect to the spline shaft 3. After the adjustment, the operating lever 10 is fastened up.
When the position of the steering wheel 10 is to be adjusted by telescopically adjusting the length of the steering apparatus, if the operating lever 10 is loosened, the steering shaft 1 which is spline-fitted in the spline shaft 3 is moved together with the steering column 2 and the outer tube 11 in the axial direction with respect to the spline shaft 3. At the same time, the fastening bolt 9 is guided along the elongated hole 8 for telescopic adjustment of the distance bracket 6.
When this outer tube 11 is to be moved in the axial direction, since the spherical bush 12 is fastened up by the O-ring 15 so that the inner peripheral surface of this spherical bush 12 is all the time in tight contact with the outer peripheral surface of the outer tube 11, the outer tube 11 is required to be moved against the tight-contacting force coming from the inner peripheral surface of this spherical bush 12.
In Japanese Utility Model Publication No. 59-43168, there is also disclosed a steering apparatus of tilt adjustment type in which the steering wheel is to be tilted. In this publication, a steering column is supported by two brackets, namely, an upper bracket and a lower bracket, and each of these two brackets has two fastening means for tilting the steering column. These two fastening means are linked together by a link mechanism in such a manner that one of the fastening means is actuated by operating the other. Since the fastening means of each bracket are operated by the link mechanism while preventing a backlash or the like caused by a vibration in high-speed running in this manner, the tilt adjustment can be performed with a simple operation.
In the steering apparatus for tilt adjustment and telescopic adjustment disclosed in Japanese Utility Model Publication No. 2-24366 mentioned above, the spherical bush 12 and the O-ring 15 are brought into slidable contact with the bush holder 13 as described above, so as to prevent a direct backlash from the outer tube 11. However, the spherical bush 12 is all the time fastened up by the O-ring 15 so that a small gap is formed between the spherical bush 12 and the bush holder 13. As a result, if a bending load with a certain measure of magnitude is applied on the steering wheel, the outer tube 11 and the like are moved to the extent of this small gap, so as to decrease the rigidity of the steering apparatus.
Though the steering shaft 1 and the outer tube 11 are moved in the telescopic operation as mentioned above, the spherical bush 12 is fastened up by the O-ring 15 in this case so that the inner peripheral surface of this spherical bush 12 is all the time in tight contact with the outer peripheral surface of the outer tube 11, the outer tube 11 is required to be moved against the tight-contacting force coming from the inner peripheral surface of this spherical bush 12, so that a large force is required as a telescopic operational force for moving the outer tube 11, etc., which results in a deteriorated operability.
Further, a surface of the bush holder 13 to be brought into tight contact with the spherical bush 12 is required to be spherically processed with accuracy, which may result in an increased processing cost.
Also, in the tilt-type steering apparatus disclosed in the above-mentioned Japanese Utility Model Publication No. 59-43168, while a backlash or the like caused by a vibration in high-speed running is prevented by use of the two brackets, the fastening means of each bracket is operated via the link mechanism, so that the tilt adjustment can be performed with a simple operation. However, it is difficult to apply such arrangement of this link mechanism as it is to a steering apparatus capable of telescopic adjustment as well as tilt adjustment.